Ice breaker for marine structures

ABSTRACT

An ice breaker for marine structures comprising a rotatably mounted plow member on an offshore platform and utilizing a vane member to position the plow member in the path of encroaching ice floes. Buoyant chambers vertically position the plow member so that the leading edge will be under or above the ice floe. High pressure fluids or mechanical saws can be used as cutting members to cut sections in the ice floe and allow the plow member to break the ice sections from the ice floe and force them above or below the remaining ice floe. High pressure jets may be located in apertures in the face of the plow member and/or located between the ice floe and the plow member. The cutting members are arranged to cut sections of ice resembling the vertical section of a truncated pyramid.

United States Patent Holder 51 Sept. 26, 1972 [541 ICE BREAKER FORMARINE STRUCTURES John E. Holder, 503 N. Central Expressway, Richardson,Tex. 75080 Filed: Oct. 2, 1970 Appl. No.: 77,506

[72] Inventor:

[56] References Cited UNITED STATES PATENTS 10/1968 Farr et al ..61/14/1868 Flannigain ..1 14/42 7/ l 970 Alexander ..1 14/41 1/1954 Brown etal. ..114/42 Primary Examiner-Jacob Shapiro Att0rney-George L. Church,Donald R. Johnson, Wilmer E. McCorquodale, Jr. and John E. Holder [5 7]ABSTRACT An ice breaker for marine structures comprising a rotatablymounted plow member on an offshore platform and utilizing a vane memberto position the plow member in the path of encroaching ice floes.Buoyant chambers vertically position the plow member so that the leadingedge will be under or above the ice floe. High pressure fluids ormechanical saws can be used as cutting members to cut sections in theice floe and allow the plow member to break the ice sections from theice floe and force them above or below the remaining ice floe. Highpressure jets may be located in apertures in the face of the plow memberand/or located between the ice floe and the plow member.

The cutting members are arranged to cut sections of I ice resembling thevertical section of a truncated pyramid.

10 Claims, 5 Drawing Figures PATENTEDSEP26 1972 FIG. 4A

2 INVENTOR JOHN E. HOLDER Ocean adjacent the North Slope.

ICE BREAKER FOR MARINE STRUCTURES BACKGROUND OF THE INVENTION Thisapplication relates to an application filed of even date herewith byJohn D. Bennett entitled METHOD AND APPARATUS FOR CUTTING ICE whichdescribes cutting ice in a manner to facilitate vertical movement of anice section in-an ice floe. The invention disclosed herein deals withthe problem of floating ice encountered in frigid waters such as theArctic Ocean, where there currently is high interest in locating anddeveloping natural resources. In the search for and development ofpetroleum from other offshore areas, platforms have been used which aresupported on the floor of a body of water. Such platforms if located inthe Arctic Islands area would be exposed to ice floes which float freelyin the water, and may be of such a size that the platform support wouldbe susceptible to damage or destruction by the severe pressures of suchan encroaching ice floe. The environment to which aplatform might beexposed if located in the Arctic region could well resemble that of theArctic The arctic Ocean adjacent the North Slope area of Alaska ischaracterized by its shallow depth and gradual slope to deep water. Airtemperaturesusually range from -31 40 F. to +50 F. The water is very.

uniform in temperature, from +28 F. to +30 F., and very saline except inthe lagoons opposite the rivers. Winds arepredominantly from the East 10to 15 mph, with a maximum of 50 to 60 knots. Waves are not usually morethan 5 feet high. In the months of November through April, large massesof ice are in continuous movement by the effects of wind in the ArcticOcean. Ice fields measuring thousands of feet in diameter are propelledin many directions by the winds and are generally unaffected by theminor currents present. I i

The main ice form in the Arctic Ocean is the ice sheet, which isgenerally 6 to 10 feet in thickness. Another form of ice encountered israfted ice, which is the term used to described the overlapping of icesheets as one sheet rides up over another sheet, resulting in an icefloe made up of two or more distinct layers. In open locations, therafting does not generally take place between sheets of more than 1 or 2feet in thickness since thick sheets cannot withstand the deflectionnecessary for one sheet to ride over the other. Rafted ice has a muchsmaller surface area than that of the more prevalent ice sheets.

Thus, it can be seen that offshore platforms located in relativelyshallow water in the Arctic Ocean will encounter ice sheets from 6 to 10feet thick, and occasionally rafted or sheet ice up to feet thick.Generally speaking, then, an offshore platform should be able toroutinely withstand at least 15 feet thick ice floes having diameters ofseveral thousand feet being moved by winds of 15 mph.

Drilling platforms may also be located in the lagoons and among theislands. Here pile-up can occur from the ice sheets impinging on longvertical surfaces. Thus in order to locate platforms in these areas,special equipment other than the equipment disclosed herein may benecessary. I

It is desirable to use offshore platforms rather than subsea systemsbecause of their availability and low cost. It is therefore an object ofthe present invention to provide methods and apparatus for equippingoffshore platforms for use in areas where ice floes are encountered.

SUMMARY OF THE INVENTION With these and other subjects in view, thepresent invention contemplates rotatably mounting a plow-like member. onan offshore platform support member and locating it relative to thewater surface by buoyant chambers so that the leading edge of the plowmember is above or below the ice floe. Cutting apparatus such asmechanical saws or high pressure jet nozzles emitting liquids are usedto cut the ice in advance of its reaching the plow member. A series ofcuts can be made to define ice sections having bottom and top surfacesof different cross-sectional areas to facilitate vertical movement ofthe ice section. A vane member, which also may act as a counterweightfor the plow member as well as a wind direction and velocity detectorare used to orient the plow-like member in the path of the-encroachingice floe.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of anoffshore platform equipped with a plow member and cutting nozzles;

FIG. 2 is an enlarged view of the plow member and cutting nozzle shownin FIG. 1;. 1

FIG. 3 is an elevational side view of the plow member and cuttingnozzles shown in FIG. 2; and

FIGS. 4A and 4B illustrate an elevational front view and sectionalelevational side view of a plow member having cutting nozzles located inthe face of the plow member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates an offshoreplatform 14 supported by a single support member 34. The support member34 is a hollow cylindrical member which extends from the floorof a bodyof water to a point above the water surface. The support member 34 alsoserves as a conduit for well pipe, and is of sufficient strength tosupport the platform and customary storage and housing facilities 15,derrick l6, and crane 17 located on the top of the platform. Sleeve 30is rotatably mounted on support member 34. Mounted on sleeve 30 are plowmember 24 and nozzle assembly 20. Plow member 24 has a center ribportion which slants downwardly toward the support member 34, andconcave side members which flare outwardly from the center rib portion.The nozzle assembly 20 includes three nozzles laterally spaced with theoutside nozzles directed angularly outward from the middle of the nozzleassembly 20. Stops 28 positioned above and below the sleeve 30 extendabout and may be welded to support member 34 and are spaced so thatsleeve 30 has room to move a short distance in a vertical direction.These stops 28 are constructed of heavy metal and describe a shoulder. Ahigh pressure fluid is emitted and directed by the nozzles in nozzleassembly 20. When this fluid impinges on ice sheet 12, the abrasiveeffect causes the cutting of such ice sheet.

As depicted in FIG. 1, ice sheet 12 is shown by passing platform 14.Plow member 24, together with nozzle assembly 20, separates two sectionsof ice 26 from the ice sheet 12. The plow member 24 is shown in aninverted position so that the leading edge of the plow member 24 is overthe ice sheet 12, and as the ice sheet 12 moves toward the platform 14,the ice sections 26 are forced downward and sideways underneath the icesheet 12 by the flared concave side members of the plow member 24.Before and during the ice sheet contact with the plow member 24, a fluidemitted by nozzle assembly cuts the ice by the fluid impinging the icesheet 12 at a high velocity and pressure. As shown herein, the nozzleassembly 20 has nozzles 22 directed so as to cut the ice in twosections. The outside nozzles 22 are angled so that the sections beingcut have a larger bottom surface than a top. surface to facilitatedownward movement of the ice sections 26.

FIG. 2 more clearly illustrates the section shown in FIG.. 1 between thestops 28, as well as showing floatation chamber 32. Flotation chamber 32is a hollow water-tight metallic member which is buoyant in water. Asshown here, inverted plow member 24 is made up of a center portion 25which first contacts the ice sheet 12 of FIG. 1. This center portion 25has a leading edge higher than its trailing edge. This forces an icesheet downwardly as it moves from the leading edge to the trailing edgeof the center portion 25. This downward force stresses the ice sheetuntil such ice sheet is split. Concave surfaces 27 of plow member 24force the broken ice sections to the side of sleeve 30 and platformsupport member 34. To aid the function of inverted plow member 24 in itstask of breaking the ice sheet, nozzle assembly 20 with nozzles 22 areplaced so that an eroding fluid exiting the nozzles 22 will contact theice sheet immediately prior to the ice sheet encountering inverted plowmember 24. Both the plow member 24 and nozzle assembly 20 are mounted onsleeve 30 which rotates on platform support member 34. The sleeve 30 islimited in its vertical movement by stops 28 located above and belowsleeve 30. Flotation chamber 32 should be positioned so. that theleading edge of the center portion 25 of the plow member 24 is locatedabove an encroaching ice sheet. In this regard, several methods can beused to determine the relationship between the inverted plow member 24and an encroaching ice sheet. Sensors for automatically determining theheight of an ice sheet could automatically activatea chain hoist,hydraulic system, or a ballast system flow control. Additionally, visualobservations can be relied upon to determine how and when to activateequipment for raising or lowering the position of the inverted plowmember 24.

Referring next to FIG. 3, a side view of the apparatus shown in FIG. 2is illustrated. Here it can be seen that the inverted plow member 24 hasa leading edge higher than its trailing edge. The leading edge projectsabove water level 42 high enough to ride over an encroaching ice sheet.The inverted plow member 24 is attached to sleeve 30 which'is raised andlowered relative to the water surface by flotation chamber 32. Sleeve 30is slidably arranged on platform support member 34. Vane member 36 alsoattached to sleeve 30, is responsive to the directional flow of water 42and therefore orients the inverted plow member 24 so that it is in thepath of encroaching ice sheets which are propelled by the sea currents.Because of the mass of the plow member necessary to force ice sheets upto 15 feet thick downwardly, the vane member 36 probably would need tobe connected to a motorized system for rotating the sleeve 30. Suchrotation can be done in any conventional manner, such as for example, bytransmittal of a directional signal from the vane member 36 to a unitlocated on the platform for rotating the plow member 24. The unit forrotating the plow member 24 might comprise a motorized tracked pullingunit wherein the track defines a circular path above the platformsupport member 34. This pulling unit can be linked to the ice breaker byflexible or rigid members. Alternatively, a pinion and shaft may be usedfor rotating the plow member 24. For ease of movement of sleeve 30,counterweight 40 is used to offset thev weight of inverted plow member24 and nozzle assembly 20 so that sleeve 30 can freely move.

A wind velocity and direction detector 56 is shown mounted oncounterweight 40. Wind velocity and direction detector 56 comprisesdirection vane 54 and wind velocity gauge 50 comprising a plurality ofcups 52. The velocity gauge and direction detector are independentlyrotatable and are connected to plow member rotational means. Like thevane member 36, information obtained from the detector 56 is transmittedas a signal to actuate the plow member rotating means. Since wind oftenis the primary moving force in propelling ice floes, the detector 56might be used exclusively in such areas of minor currents. Where bothsea current and wind affect ice floe movement, a composite signal mightbeused to activate means for rotating the plow member 24.

Locking devices can be used which are responsive to forces being appliedagainst inverted plow member 24 so that the plow member will not. bepushed sideways by an encroaching ice sheet. A typical locking devicecould consist of a reinforced ribbed metal cover immovably mountedbetween the platform support member 34 and the sleeve 30. The ribbedcover would extend around and completely encircle the support member 34and the vertical ribs would be closely spaced so that the sleeve 30could freely rotate thereon. Several pivotable metal rods hydraulicallyactuated and attached in slots in the sleeves 30 could be pivoted toengage the ribs for locking the plow member 24 into position. Such alocking device has not been shown. Stops 28 prevent excessive verticalmovement caused by the ice sheet forcing the inverted plow member 24 uptoo high to be operational. Also, lower stop 28 prevents the loss ofsleeve 30 and related inverted plow member 24,'nozzle assembly 20,etcQif the flotation chamber 32 was damaged and no longer operational.Alternatively or additionally, cables attached to the platform and icebreaker assembly could be used to prevent the loss of the ice breakerassembly. Nozzle assembly 20 has nozzles 22 located above and in advanceof inverted plow member 24 so that its cutting action is utilized inadvance of the ice sheet reaching inverted plow member 24. Pump assemblymeans 18 is shown adjacent to the nozzle assembly 20, but can be placedin any appropriate location, and is used to pump fluid to the nozzles.

FIG. 4 illustrates an alternative embodiment of the plow member andnozzle assembly. FIG. 4A is a side view of a plow member 24 and relatednozzle assembly 20. Here, as in FIGS. 2 and 3, the nozzles 22 arelocated above the plow member 24. Additionally, nozzles 38 are locatedin the face of the plow member 24. As illustrated here, the plow memberis in an upright position rather than inverted. This is betterillustrated in FIG. 43. There the nozzles 22 include a pair of outsidenozzles angled inwardly rather than outwardly as previously illustratedin FIG. 2. Because of the upright position of the plow member 24, theice sheet will ride up on the center portion of the plow member 24 tofacilitate movement of a broken ice section in an upward direction; theoutside nozzles 22 are directed inwardly so that the ice sections willhave a larger top surface than a bottom surface. Flotation chamber 32maintains the plow member 24 in appropriate position relative to anencroaching ice sheet. As illustrated here, there is a nozzle shownbetween outside inwardly directed nozzles 22 which may be eliminatedbecause of nozzles 38 located in the face of plow member 24 on themid-portion 25. Alternatively, the nozzles can be eliminated altogetheror used singly or in multiples.

While particular embodiments of the present invention have been shownand described, it is apparent that changes and modifications may be madewithout departing from this invention in its broader aspects, andtherefore, the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

1. Apparatus for protecting an offshore platform supported on asubstructure from encroaching ice floes, comprising: an inverted plowmember having a central ridge portion and concave shoulders rotatablymounted on the offshore platform substructure and positioned such thatthe leading edge of the plow member is located above the ice floe; andat least one cutting member attached to the offshore platform andpositioned relative to said plow member so that the cutting membercontacts the ice floe adjacent the plow member.

2. The apparatus of claim 1 including means for rotating the plow memberand cutting member which is responsive to elements responsible for thedirection of movement of the ice floes.

3. Apparatus for protecting a platform located in water from ice floesin said water, comprising: a plow member having a central ridge portionand concave shoulders which is rotatably mounted on the offshoreplatform and located adjacent the water surface; and cutting meanslocated adjacent the plow member, including high pressure liquid nozzlesdirected toward the ice floe. I

4. The apparatus of claim 3 wherein the plow member is in an invertedposition, having the leading edge positioned above the trailing edge sothat ice contacting the plow member is deflected downwardly.

5. The apparatus of claim 3 including means for orienting the plowmember which is responsive to direction of movement of the ice floes.

6. The apparatus of claim 3 wherein the cutting means includes means forforcing a liquid at high pressure through said nozzles.

7. The apparatus of claim 3 wherein said cutting means is arranged tocut the ice floe so that the cutting planes define ice sections having atop and bottom surface of substantially different cross-sectionalsurface areas.

8. The apparatus of claim 3 wherein the ice cutting means are jetnozzles directed through apertures in the face of the plow member.

9. The apparatus of claim 3 including buoyant members attached to saidplow member for maintaining the plow member adjacent the water surface.

10. Method of protecting an offshore structure from encroaching icefloes comprising the steps of: locating a plow member between thestructure and the encroaching ice floe; directing high pressure streamsof liquid against said ice floe, at various angles to provide cuttingplanes which define ice sections having top and bottom surfaces ofdifferent cross-sectional areas; and removing the ice sections from theice floe.

1. Apparatus for protecting an offshore platform supported on asubstructure from encroaching ice floes, comprising: an inverted plowmember having a central ridge portion and concave shoulders rotatablymounted on the offshore platform substructure and positioned such thatthe leading edge of the plow member is located above the ice floe; andat least one cutting member attached to the offshore platform andpositioned relative to said plow member so that the cutting membercontacts the ice floe adjacent the plow member.
 2. The apparatus ofclaim 1 including means for rotating the plow member and cutting memberwhich is responsive to elements responsible for the direction ofmovement of the ice floes.
 3. Apparatus for protecting a platformlocated in water from ice floes in said water, comprising: a plow memberhaving a central ridge portion and concave shoulders which is rotatablymounted on the offshore platform and located adjacent the water surface;and cutting means located adjacent the plow member, including highpressure liquid nozzles directed toward the ice floe.
 4. The apparatusof claim 3 wherein the plow member is in an inverted position, havingthe leading edge positioned above the trailing edge so that icecontacting the plow member is deflected downwardly.
 5. The apparatus ofclaim 3 including means for orienting the plow member which isresponsive to direction of movement of the ice floes.
 6. The apparatusof claim 3 wherein the cutting means includes means for forcing a liquidat high pressure through said nozzles.
 7. The apparatus of claim 3wherein said cutting means is arranged to cut the ice floe so that thecutting planes define ice sections having a top and bottom surface ofsubstantially different cross-sectional surface areas.
 8. The apparatusof claim 3 wherein the ice cutting means are jet nozzles directedthrough apertures in the face of the plow member.
 9. The apparatus ofclaim 3 including buoyant members attached to said plow member formaintaining the plow member adjacent the water surface.
 10. Method ofprotecting an offshore structure from encroaching ice floes comprisingthe steps of: locating a plow member between the structure and theencroaching ice floe; directing high pressure streams of liquid againstsaid ice floe, at various angles to provide cutting planes which defineice sections having top and bottom surfaces of different cross-sectionalareas; and removing the ice sections from the ice floe.